Gas constituency audible indicating device



March 7, 1950 v. wouK ETAL GAS CONSTITUENCY AUDIBLE INDICATING DEVICE lFled July 27, 1945 .in w e M, f 3 6 f j r h wa c .r .M W mf H r. e awk Ra V. m b *E mmm m vuqfm ma. T W fm? y ,mbH 5 .Cl ww W u c w WITNESSES: W

Patented Mar. 7, 1950 GAS CONSTITUENCY AUDIBLE INDICATING DEVICE Victor -Wouk s and Wilson M. rBrubaken. Pitts- Ebuxgh,..1? a., vassignors to Westinghousev..Electric ."ner Adiscerniblexby the v-eyeof anwopera-tor. i some cases, however, 'discernment' of a change in I surroundings.

',Corporation,1.EastflPittsburgh, Pa., a corporation of Pennsylvania ApplicationJuly'Z, 1945;?SerialNo. 607,406

2 L Claims.

This nventionrelates tov devices responsive to a' change in condition-and it hasparticular relation to' gauge ,assemblies responsivehto a` change in theconstituency ci a-gaseous medium, suchas the contents. oianvacuum system.

'Devices responsive tov a change-fin condition must indicate the `Changein somereadily disncernible manner. 4Inprior artzpractice-itfhas 4been common to :employ-indicating instruments for indicating the change in condition in :a man- In condition by the eyeA of'anoperator is inconvenient. Forlthe purpose of'disoussion, the invention willA be considered with respect to a Agauge device designedfto depict thefchange inA condition oi 1a gaseousmedium, suchas the contents oina vacuum system. When agaugefdeviceisfemployed in locating leaks present: inzafvacuumsystem, it is common practiceA for aiirst operator to apply a suitable material, suchA as algas, to the suspected portion orl the vacuumvsystem. If e a leali is present atthis point,xthe appliedI material produces a change in the gaseousmedium within the vacuum system or a decrease inwthe' pressure within the vacuum system. y"Thischangein condition of lthe `contents .of the vacuum system `is `accompanied in a change inthe reading of the indicating instrument included the associated gauge device. The :change in vreading of' thein dicating instrument is noted by a secondiobserver who reports the ichange'to the rstxobserver.

This technique requiresA two vobservers and'isinconvenient. 'Ii desired: an extension Icord .may

be employed for the indicating instrument to permit its location adjacent the iirstobserver. vThis would require a division of lhis attention.

Consideration has been given to=the replacement oi the indicating instrument'fzbyia'trans 'the change incondition. ochangesjn gambi-.the =amplers1may beidueto"variationsiin temperature or changes in elements of` theamplifier.

Inaccordance with the invention `a change in condition is depicted by achange in pitch orireduency of soundfemittedby a transducer. Such ya change in pitch is read-ily discernible Vby an op- I erator. Notonly is the ear sensitive to variations inthe pitch of sound but `such variations may r in condition.

.It is a: further object of the invention toprovide a gauge device for depicting a change in/the vconstituency `of agaseous medium by means of a change in pitch `or irequencyo sound emitted by a transducer.

Other objects `of .the invention will be apparent from: the following description taken in conjunction with the `accompafnying drawinglin-which the single figure is a schematic view of a system embodying the invention.

Referring tothe drawing, the single figure lshows a gauge devi-ce suitable for detecting a .changer in' the constituencyof a gaseous medium contained 'within la. vacuum system I. -The'device includes lal gauge unit which may be of any desired type capable of producing lanoutput dependent on the change in condition vwhich is to be determined. If the gauge unit is to be re- 'sponsive-toa change in constituency of the contents of the yvacuum system l, it may, for exvample-take the form of an ionization gauge or a Piranigauge. Such gauges are-well known in the-art, and 4a discussion-thereof and `of leak hunting maybe ioundin e. bookentitled-Producer capable .of producing an .audible sound 1., lcedures in Experimental Physics by John Strong, which varies in amplitude in accordance withi the published by Prentice Hall, Incorporated. New change in conditionl ofthe contentstoithevacu- York. 1938. If desired. a mass spectrometer leak `um system. Such a transducerhas atleast ytwo hunter'fmay be employed as vthe gauge unit.3.

objectionable characteristics. Itis dini-cult to The output ofthe-gauge unit 3 is employed detect changes'in;amplitude of isoundin noisy in for controlling 'the frequency of oscillation of an oscillation generator 5. This l oscillation gen- `eratormay` be. of 'any desired construction capableoi' producinga frequency ofoscillation which is responsive to thel input to the oscillationfgen- Herator from the gaugerunit. If the output of ythe gauge unit 3 v is Vinsunicient lto control the oscillation-:generator 5, an amplifier yI 4of Aconvenctional construction maybe Vinterposed between employed for controlling the energization of a transducer 9 which may be in the form of earphones or a loudspeaker. Consequently, the pitch or frequency of the sound emitted by the transducer 9 is a function of the change in condition to be determined. If the output of the oscillation generator is insufficient to energize adequately the transducer 9, an amplifier II of any suitable construction may be interposed between the oscillation generator and the transducer' 9.

In order to illustrate the invention more particularly, speciiic circuit elements are illustrated for each component of the gauge device. Certain sources of energy for the gauge device are depicted by polarity markings. For example, positive terminals I3, I5, I1 and I9 are shown which have a common negative terminal 2I associated therewith. This negative terminal may be grounded. The positive terminals may represent separate sources or a common source of energy associated with the gauge device.

The gauge unit 3 conveniently may take the form of a standard Pirani gauge. The Pirani gauge includes two substantially equal resistors 23 and 25 which have substantial temperature coefficients of resistance. The resistor 23 may be enclosed in a high Vacuum, and the resistor 25 may be enclosed in a container which is connected through a duct 21 to the vacuum system which is to be studied. Consequently, the atmosphere surrounding the resistor 25 will depend upon the constituency of the gas present within the vacuum system I. The resistors 23 and 25 are associated with two resistors 29 and 3| to form a Wheatstone bridge. Energy for the bridge is supplied from a suitable source, such as a battery 33. The output of the Wheatstone bridge is applied across the potentiometer PI.

If desired, the output of the Wheatstone bridge may be amplied in any suitable manner. As shown on the drawing, an electron triode tube 35 may be employed for this purpose. This triode has a plate electrode 35a, a control electrode 35h and. a cathode 35e. An adjustable bias is applied between the control and cathode electrodes of the triode by means of a potentiometer P2 which is connected across a suitable source of energy, such as a battery 31. For the specic tube hereinafter set forth, the potentiometer P2 may be connected to apply a negative bias to the tube 35. The voltage between the movable tap on the potentiometer PI and ground also is included in the control electrode circuit of the triode 35. control and cathode electrodes of the triode 35 is the sum of the bias voltage applied by the potentiometer P2 and the portion of the Wheatstone bridge output which is supplied rom the potentiometer PI. The control electrode 35h is connected to the potentiometer P2 through a gridresistor RI. The plate electrode 35dI of the triode is connected through a plate resistor R2 to an intermediate point on a voltage divider formed by two resistors R3 and R4. The output of the amplifier 1 is applied through a resistor R5 to the oscillation generator 5. It should be noted that the amplifier 1 is essentially a direct-current or direct-coupled amplier.

The oscillation generator 5 may take the form of a relaxation oscillator employing a gaseous discharge tetrode 39 of the type commonly referred to as a thyratron. This tetrode includes a plate electrode 39a, a control electrode 33D, a shield electrode 39d and a cathode electrode 39a.

Consequently, the Voltage between the A bias voltage is introduced in the control elec trode circuit of the tetrode 39 in any suitable manner. For example, this bias may comprise the voltage drop across a neon glow tube 4I, which is energized from the terminal I1 through a voltage dropping resistor R1. A bypass capacitor CI is connected across the neon glow tube. The shield electrode 39d is connected to the cathode through a resistor R6, and the control electrode 39D is connected to the plate of thc triode 35 through the resistor R5.

The voltage applied between the plate and cathode electrode of the tetrode 39 is determined in part by the voltage across a capacitor C2 which is connected to the plate electrode 39a, through an inductance LI. The capacitor C2 is charged from the terminal I5 through a decoupling filter 43 which includes a resistor R9 and a capacitor C4. 'Ihe rate of charge of the capacitor C2 is determined substantially by a resistor R8.

Relaxation oscillators are well known in the art. As is well understood, the capacitor C2 charges until the voltage thereacross together with the voltages applied to the control electrode of the tetrode 39 are sufficient to initiate a discharge of the capacitor C2 through the tetrode. Upon completion of this discharge operation, the capacitor C2 again is charged. This cycle is repeated indefinitely to provide an alternating output.

As previously pointed out, the output of the oscillation generator is employed for controlling the energization of the transducer 9. Ordinarily, it will be desirable to include the amplifier II between the transducer and the oscillation generator. In the specific embodiment shown on the drawing, the ampliiier II includes a triode 45 having a plate electrode 45a, a control electrode 45h and a cathode 45o. The output of the oscil lation generator is coupled through a coupling capacitor C3 across a potentiometer P3. The adjustable tap of the potentiometer P3 is connected through a grid resistor RID to the control electrode 45h of the triode. The triode is self-biased by means of a cathode resistor RI I which has a bypass capacitor C5 connected thereacross. The plate electrode 45a is connected to the terminal I9 through the primary of an output transformer 41 and a resistor RI2. The secondary of the output transformer 41 is connected to the transducer 9.

It is believed that the operation of the device shown in the drawing is apparent from the foregoing discussion. With the gauge unit 3 proportioned for zero output or a predetermined output as desired, the proportion of the output of the gauge unit which is selected before amplification is determined by the setting of the tap on the potentiometer PI. The setting of this tap determines the change in frequency of the oscillation generator relative to the change in output of the gauge unit. Consequently, the potentiometer PI may be termed a sensitivity control. The potentiometer P2 may be adjusted to determine the frequency of the oscillation generator when the gauge unit 3 is in its balanced or predetermined normal condition. In practice it has been found convenient to adjust the potentiometer P2 for a frequency output of the order of cycles per second. If the frequency of 60 cycles per second is selected, a change in the output of the gauge unit 3 may suffice to interrupt completely the oscillation normally produced by the oscillation generator. This interruption of oscillation is very readily noted by the observer. The amplitude of the sound emitted by the transducer 9 may be adjusted by variation in the setting of the tap on the potentiometer P3. Consequently, the potentiometer P3 may be termed a manual volume control.

After the device has been properly adjusted, an operator may attempt to locate leaks in the vacuum system I as by spraying gas over suspected areas of the system. If a leak is present, the output of the gauge unit varies. In turn, the variation in output of the gauge unit results in variation of the frequency of oscillation of the oscillation generator and the pitch of the sound emitted by the transducer 9. If the output of the gauge unit varies in such a direction as to increase in a positive direction the voltage applied to the control electrode l35h of the trode 35, the frequency of the oscillation generator and the pitch of the sound emitted by the transducer 9 decreases. Conversely, as an output of the gauge unit 3 changes to decrease the positive voltage of the control electrode 35h relative to the associated cathode, the frequency of the oscillation generator and the pitch of the sound emitted by the transducer 9 increase. Since the ear is sensitive to such frequency variations, the operator readily ascertains the presence oi a leak. It should be noted that the pitch of sound emitted by the transducer 9 is substantially independent of the gain of the amplifier Il. Moreover, the operator can discern changes in pitch of sound emitted by the transducer despite the presence of the appreciable background noise.

Although the components of the gauge device may vary appreciably, the triodes 35 and 45 may comprise respectively a type GSNTGT tube and a type GA3 tube. The gaseous discharge tetrode 39 may be a type 2051 tube. When these tubes are employed, the following additional values may be adopted:

P1=5 megohms 132:2 megohms Ps=200,000 ohms R1=2 megohms R2=0.2 megohm R3, R4=25,000 ohms R5=0.1 megohm R=0.5 megohm R7=0.4 megohm Rs=0.5 megohm R9=10,000 ohms R1o=0.1 megohm R11=1,000 ohms R12=500 ohms 01:0.1 mid. 02:0.004 mid. 03:0.005 mid. 04:8 mfd.

Cs= mid. Battery 91:7.5 volts L1=30 millihenries terminals I3, I5, Il and I 9:300 volts to ground {With a gauge device of this type an input change of 140 of a volt produces a change in pitch of sound emitted by the transducer 9 which can be readily discerned.

Although the invention has been described with reference to certain specic embodiments thereof, numerous modifications are possible. Therefore, the invention is to be restricted only 6 by the appended claims as interpreted in view of the prior art.

We claim as our invention:

1. In a device for representing a change in the constituency of a gaseous medium, a gauge responsive to the constituency of a gaseous medium for producing a direct electrical voltage having an amplitude dependent on the deviation of the gaseous medium from a :predetermined constituency, a relaxation oscillator comprising a gaseous discharge tube, said tube having a control electrode responsive to a direct electrical quantity for controlling the frequency of the relaxation oscillator, means for energizing said control element in accordance with the amplitude or the electrical voltage, electroresponsive transducer means for producing a sound output, and means for energizing said transducer means in accordance with the generator oscillator output to produce sound having a pitch controlled by the frequency of the oscillator output, said control electrode being biased to a value differing only slightly from the value required to stop oscillation of said relaxation oscillator, whereby a slight change in the constituency of the gaseous medium from said predetermined constituency results in a cessation of sound from the transducer means.

2. In a device for representing a change in the constituency of a gaseous medium, a gauge responsive to the constituency of a gaseous medium for producing a direct electrical voltage having an amplitude dependent on the deviation of the gaseous medium from a predetermined constituency, an electrical oscillation generator having a control element responsive to a direct electrical quantity for determining the frequency of alternation of the generator output, means for energizing said control element in accordance with the amplitude of the electrical voltage, transducer means for producing a sound output, and means for energizing said transducer means in accordance with the generator output to produce sound having a pitch controlled by the frequency of alternation of the gener ator output, said generator control element being biased to a value differing only slightly from the value required to produce substantially no sound from the transducer means, whereby a slight change in the constituency of the gaseous medium results in a substantial cessation of sound from the transducer means.

VICTOR WOUK. WILSON M. BRUBAKER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,304,208 Shakespeare May 29, 1919 1,881,394 Aull Oct. 4, 1932 1,965,147 Marvel July 3, 1934 1,999,215 Smith Apr. 30, 1935 2,004,662 Junkers June 1l, 1935 2,295,570 Dunmore Sept. 15, 1942 2,378,395 Dickson June 19, 1945 2,383,321 Kleber Aug. 21, 1945 2,395,368 Bull Feb. 19, 1946 

